By 1825, platina ore of commerce was commonly assumed by Americans, from English scientists (William Phillips?) to have Specific Gravity 15.6. Citation: Manual of Mineralogy and Geology: Designed for the Use of Schools... Ebenezer Emmons (1826)

c.1812 (1818): c.1814 (1815):1824-6:Reportedly, Anthony Plantou introduced porcelain teeth to America. He arrived in the USA from Paris in 1817 and began the manufacture circa 1820.

In 1822, Charles W. Peale was not the first to employ Platinum pins, but he was likely the first American to do so. (He was not a dentist.)

It follows that Plantou's 'scarcity of platina' refers to experiments carried out in 1824-6 for this patent application made in 1826 or 1827 and granted on April 5, 1828.